Aerobic oxidative synthesis of quinazolinones and benzothiazoles in the presence of laccase/DDQ as a bioinspired cooperative catalytic system under mild conditions.

Nadia Ghorashi,Amin Rostami,Reza Moradi,Amira Abdelrasoul,Zahra Shokri

doi:10.1039/c9ra10303a

Nadia Ghorashi, Amin Rostami + Show 3 more

Open Access

https://doi.org/10.1039/c9ra10303a

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Abstract

The current study applied laccase/DDQ as a bioinspired cooperative catalytic system for the synthesis of quinazolinones (80–95% yield) and benzothiazoles (65–98% yield) using air or O2 as ideal oxidants in aqueous media at ambient temperature. The aerobic oxidative cyclization reactions occur in two steps: (i) chemical cyclization; (ii) chemoenzymatic oxidation. These methods are more environment-friendly, efficient, simple and practical than other reported methods due to the use of O2 as an oxidant, laccase as an eco-friendly biocatalyst, aqueous media as the solvent and free from any toxic transition metal and halide catalysts. Therefore, these methods can be applied in pharmaceutical and other sensitive synthetic procedures.

Highlights

The cyclization of o-anthranilamides with aldehydes followed by subsequent oxidation is the most convenient method for the synthesis of these valuable compounds.[3,4]
In continuation of our study in the catalytic applications of laccase enzyme in the aerobic oxidation of organic compounds,[20] we report the aerobic oxidative synthesis of quinazolinones and benzothiazoles in the presence of laccase/DDQ catalyst system
The oxidative cyclization synthesis of quinazolinones occurs in two-step sequence: (i) chemical cyclization of o-anthranilamide with aldehyde in the presence of sulfamic acid to afford 2,3dihydroquinazolin-4(1H)-one (ii) chemoenzymatic aerobic oxidation of 2,3-dihydroquinazolin-4(1H)-one in the presence of laccase/DDQ catalyst system (Scheme 1)

Summary

Introduction

Quinazolin-4(3H)-ones are important nitrogen-containing heterocycles which have various biological and medicinal activities, including antibacterial, anticancer, antimicrobial, antidiabetic, antifungal, anticonvulsant and antiallergy.[1,2] The cyclization of o-anthranilamides with aldehydes followed by subsequent oxidation is the most convenient method for the synthesis of these valuable compounds.[3,4]. Quinones have been applied as oxidants in organic chemistry and hydride acceptors in biological processes.[9] Among quinones, 2,3-dichloro-5,6-dicyano-1,4-benzoquinone (DDQ) is well-known as an effective and readily available oxidant for numerous organic transformations.[10,11,12] In spite of the utility of DDQ as a stoichiometric oxidant, its high toxicity and cost, the isolation problem because of the concomitant by-product DDQH2 are the main issues associated with utilizing DDQ on a large scale To overcome these disadvantages, a combination of the catalytic amount of DDQ and a less expensive co-oxidant that regenerate DDQ from its reduced hydroquinone form have been developed.[13,14,15] Recently, the catalytic oxidation systems using catalytic amounts of DDQ and a co-catalyst in the presence of molecular oxygen as a terminal oxidant have attracted more attention.[16,17,18] these procedures have been successfully applied in the eld of aerobic oxidations, the development of an alternative method which is green and employing eco-friendly co-catalyst such as biocatalysts in combination with DDQ for the aerobic oxidation of organic compounds is in demand. Scheme 1 Aerobic oxidative cyclization synthesis of quinazolin-4(3H)-ones

Results and discussions

Determination of the activity of laccase from Trametes versicolor

General procedure for the synthesis of quinazolinone derivatives